Hello, All!

Специальный форматер для вывода размеров файлов (10КB, 1,5MB, etc).
Объединяя идеи Гайдара и Joshua Flanagan.

Использовать

class Program

{

    static void Main(string[] args)

    {

        Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs3}", 100));

        Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 2000));

        Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs1}", 30000000));

        Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 400000000000));

    }

}

Результат

File size: 100.000B
File size: 1.95KB
File size: 28.6MB
File size: 372.53GB

Исходник

using System;
using System.Text;

namespace Rsdn.Framework.Common
{
 public class FileSizeFormatProvider : IFormatProvider, ICustomFormatter
 {
  public object GetFormat(Type formatType)
  {
   if (typeof(ICustomFormatter).IsAssignableFrom(formatType))
    return this;

   return null;
  }

  private const string fileSizeFormat = "fs";
 
  private string[] letters = new string[] { "B", "KB", "MB", "GB", "TB", "PB" };

  public string Format(string format, object arg, IFormatProvider formatProvider)
  {
   if (format == null || !format.StartsWith(fileSizeFormat))
   {
    return defaultFormat(format, arg, formatProvider);
   }

   Decimal size;
   try
   {
    size = Convert.ToDecimal(arg);
   }
   catch (InvalidCastException)
   {
    return defaultFormat(format, arg, formatProvider);
   }

   byte i = 0;
   while ((size >= 1024) && (i < letters.Length - 1))
   {
    i++;
    size /= 1024;
   }

   string precision = format.Substring(2);
   if (String.IsNullOrEmpty(precision)) precision = "2";

   return String.Format("{0:N" + precision + "}{1}", size, letters[i]);

  }

  private static string defaultFormat(string format, object arg, IFormatProvider formatProvider)
  {
   IFormattable formattableArg = arg as IFormattable;
   if (formattableArg != null)
   {
    return formattableArg.ToString(format, formatProvider);
   }

   return arg.ToString();
  }
 }
}